VoxelSniper is the premier long range map editing tool for Minecraft.

This mod allows you to edit any block that you can see using an arrow (for replacing) and a gunpowder (for adding). It is best used by those with a strong attention to detail and fits a wide array of applications, from making detailed edits to structures with the snipe brush, to making massive terraforming jobs a breeze with some of the earth shattering soft selection tools.

Plugin Link:

https://dev.bukkit.org/projects/voxelsniper